The war in Ukraine has delivered a shock to global energy markets. Now the planet is facing a deeper crisis: a shortage of food.

A crucial portion of the world’s wheat, corn and barley is trapped in Russia and Ukraine because of the war, while an even larger portion of the world’s fertilizers is stuck in Russia and Belarus. The result is that global food and fertilizer prices are soaring. Since the invasion last month, wheat prices have increased by 21 percent, barley by 33 percent and some fertilizers by 40 percent.

The upheaval is compounded by major challenges that were already increasing prices and squeezing supplies, including the pandemic, shipping constraints, high energy costs and recent droughts, floods and fires.

Now economists, aid organizations and government officials are warning of the repercussions: an increase in world hunger.

The looming disaster is laying bare the consequences of a major war in the modern era of globalization. Prices for food, fertilizer, oil, gas and even metals like aluminum, nickel and palladium are all rising fast — and experts expect worse as the effects cascade.

“Ukraine has only compounded a catastrophe on top of a catastrophe,” said David M. Beasley, the executive director of the World Food Program, the United Nations agency that feeds 125 million people a day. “There is no precedent even close to this since World War II.”

Ukrainian farms are about to miss critical planting and harvesting seasons. European fertilizer plants are significantly cutting production because of high energy prices. Farmers from Brazil to Texas are cutting back on fertilizer, threatening the size of the next harvests.